Two selection strategies of epiphitic native yeasts with potential biocontrol capacity against postharvest pears pathogens in Patagonia

LUTZ, C.; ROBIGLIO, A.; SOSA, C.; LOPES, C.A.; SANGORRÍN, M.P

Neuquén, Argentina

Simposio; XI Simposio Internacional de Peras.; 2010

International Society for Horticultural Science

To reduce the use of fungicides, biological control with yeasts has been proposed.In order to find antagonistic yeasts adapted to pear storage conditions (0/-1ºC for 7months), two isolation strategies were explored. In 2007 (strategy A), the yeastswere isolated from the surface of healthy fruits. Aliquots of the obtainedsuspensions were seeded on GPY agar and incubated at 26ºC. In 2008 (strategyB), washings from healthy wounds after 150 days at 0ºC were used to inoculatefresh pears wounds with Penicillium expansum. Yeasts were isolated from healthywounds after 50 days of incubation in cold, by seeding on GPY agar plates. Fromboth A and B isolation strategies, one isolate from each yeast species was testedfor antagonistic activity against P. expansum and Botrytis cinerea by in vivo (pearwounds at 0ºC) and in vitro (dual cultures at 20ºC) assays. By means of strategyA, six different yeast species were identified: Aureobasidium pullulans, Pichiaphilogaea, Cryptococcus difluens, Cryptococcus albidus, P. membranifaciens andRhodotorula mucilaginosa. Among them, the best antagonists were A. pullulansand R. mucilaginosa, which reduced only P. expansum disease incidence (33%).Nine different species were obtained from strategy B: A. pullulans, Cryptococcustephrensis, Cryptococcus victoriae, P. membranifaciens, Rhodotorula glutinis,Candida patagonica and Cryptococcus weringae. C. victoriae showed the higherantagonistic activity against both pathogens, including 0% of P. expansum diseaseincidence. Differences between in vivo and in vitro biocontrol assays wereobserved. In in vitro assays, all yeasts produced a greater growth inhibition of P.expansum than that produced on B. cinerea, but yeast from strategy A reachedhigher inhibition values (50%). The strategy B, based on the utilization of fruithealthy wounds in cold storage conditions was the most effective strategy for theselection of antagonistic yeasts for postharvest diseases control